1. Field of the Invention
The present invention relates to a device and method for stimulating muscles. More particularly, the invention relates to a device and method for stimulating muscles to maximize muscular development while minimizing required physical exertion and stress on the muscles, respiratory system, and cardiovascular system.
2. Description of the Related Art
Existing exercise machines generally provide a means for offering resistance to voluntary movement of various limbs of the body, or in some devices, provide a means for imparting motion to various parts of the human body when the body is in a relaxed, passive state. U.S. Pat. No. 5,273,028 to McCleod et al. (McCleod) discloses a method and apparatus that allegedly promotes bone tissue growth by imparting a mechanical load to the bone tissue. The McCleod device includes upper and lower rigid plates with spring means positioned between the plates to support the upper plate relative to the lower plate, and dynamic force transducers positioned between the plates to vertically drive the upper plate with respect to the lower plate. The spring means between the plates is selected such that the natural frequency of the device in combination with a body positioned on the upper plate will fall into the range between 10 and 50 Hz. The upper plate always remains parallel to the lower plate, with the peak-to-peak vertical displacements imparted by the dynamic force transducers between the plates being limited to no greater than 2 mm such that the strain induced on a body positioned on the upper plate will not exceed 500 microstrain. McCleod discloses that in order to minimize the chance of injury to the patient and bone tissue being treated, the peak-to-peak dynamic acceleration imparted to the body by the device should not exceed 0.3 g (corresponding to a peak-to-peak displacement of 2.0 mm). The McCleod device and method is designed to drive the combination of the upper plate and a body standing on the upper plate in a vertical direction and at its natural resonant frequency. The sole purpose of the McCleod device is to generate a load on the bone tissue that mimics a load generally created on the bone tissue by certain muscle contractions. The McCleod device does not provide any beneficial development of the muscles themselves or of the neural patterns characterizing normal patterns of movement of the body.
Soviet Union Publication 1344356 (SU ""356) discloses a method of stimulating muscles using a combination of electrical and vibration stimulation. SU ""356 does not disclose an apparatus for performing the stimulation other than to indicate that a cord and block attached to a vibro-stimulator can be used in order to raise a limb up to an accessible position. The vibro-stimulation is always performed on the muscle-antagonist, while the electro-stimulation is performed on the muscle-synergist (muscle-protagonist). A user of the method taught by SU ""356 flexes a muscle while synchronized vibration and electrical stimulation is conducted. The vibro-stimulation is transferred to the muscle-antagonist in order to assist in expansion of the muscle-antagonist. Under the influence of vibro-stimulation, an increase in the amplitude of the expansion of the muscle-antagonist takes place, while under the influence of electro-stimulation, the concentric contraction of the muscle-synergist (or muscle-protagonist) increases, which leads to an increase in the active and passive mobility of the area around the muscles.
U.S. Pat. No. 3,540,436 to Hueftle (Hueftle) discloses a machine having a pair of vertically movable footboards that are arranged parallel to each other with the bottoms of the rear ends of each of the footboards riding on rotatable cams that provide alternating reciprocating vertical movement of the footboards. The alternating movement of the footboards is performed to simulate a walking motion and is therefore performed at a very low frequency. The amount of vertical movement of the rear ends of the footboards is limited by the eccentricity of the rotatable cams, and therefore the only adjustment of amplitude of movement for a user is achieved by the user moving closer to or farther away from the rear ends of the footboards.
U.S. Pat. No. 5,500,002 to Riddle et al. (Riddle) discloses a passive motion physical therapy device having a centrally located body support member for supporting the buttocks of a patient and hingedly attached support members on both sides of the centrally located body support member for supporting the upper and lower torso of the patient. Two actuators driven by a single motor are provided with displacement cams that allow the upper and lower torso support members to be simultaneously oscillated either in phase or out of phase. The device taught by Riddle is simply a passive motion physical therapy device that moves portions of the body of a patient without resulting in any contraction of the muscles.
U.S. Pat. No. 5,755,651 to Homyonfer et al. (Homyonfer) discloses an exercise device having a plate that can be pivoted about a central axis with energy absorbing elements connected to both ends of the plate to provide a desired degree of resistance to pivotal movement of the plate about its central axis. A user of the Homyonfer device places at least one foot on the pivotal plate with a heel toward one end of the plate and the toes toward the opposite end of the plate. An exercise movement consists of raising the heel and applying pressure with the toes or applying pressure with the heel and raising the toes. The user exercises by applying a moment to the pivotal plate against the resistance of the energy absorbing elements.
U.S. Pat. No. 850,938 to Kellogg (Kellogg) discloses a dumbbell housing an electric motor that drives a shaft connected to an eccentric mass such that when the shaft is rotated by the motor the dumbbell is vibrated.
None of the conventional exercise machines provide a method or device for stimulating a muscle or group of muscles in the proper manner to promote rapid development of the muscles while minimizing stress on the musculature, respiratory and cardiovascular systems. Existing exercise machines also do not provide a means for stimulating muscles in a manner that allows for rapid development of the neural patterns associated with a body""s natural movements.
In view of the deficiencies of the above-discussed related art devices, the present invention has been developed to stimulate muscles in a manner that promotes rapid development of the muscles while minimizing the need for conscious exertion and minimizing stress on the musculature, respiratory and cardiovascular systems. The invention invokes a muscle""s natural involuntary, reflexive response or stretch reflex by imparting a sudden increase in load on the muscle over a defined period of time from a predetermined base load at which the muscle has assumed a baseline tonus, and over a predetermined amplitude of motion. The stimulation of an involuntary reflexive response or stretch reflex of the muscle can be repeated many times over a relatively short period of time, yielding substantial benefits in muscular development as well as development of the neural patterns associated with various movements of various parts of the body.
The method of stimulating muscle according to an aspect of the present invention maximizes the rate of development of the muscle while minimizing strain. Activation of a muscle or a group of muscles occurs by increasing a force input to the muscle or group of muscles from a baseline force at which the muscles have assumed a desired baseline tonus to a peak force over a predetermined period of time and while moving the muscles through a predetermined amplitude of motion. The input force is then reduced from the peak force back to the baseline force, where it is maintained for a predetermined time interval before a subsequent activation.
The time for activation of the muscles from a baseline input force to the peak force and back to the baseline force is predetermined in order to stimulate the muscles"" involuntary natural reflexive responses or stretch reflexes. The various muscles of the body used in performing normal movements such as walking or running exhibit their natural reflexive responses as a body maintains its balance through proprioception, or the unconscious perception of movement and spatial orientation arising from stimuli within the body such as tensions within the tissues of the body. When a force is input to a portion of a body, muscles connected through tendons to that portion of the body can influence the resulting motion of that portion of the body. The muscles that contract in a stretch reflex to act directly against the input force are the muscle-protagonists, while the muscles that must expand in order to allow the portion of the body to move against the input force are the muscle-antagonists.
If a force acts on a muscle or group of muscles, imparting a predetermined amount of movement to the affected muscles, and then is removed over a proper period of time, the muscle-protagonists react by contracting and the muscle-antagonists expand in involuntary reflexive responses or stretch reflexes. According to an aspect of the present invention, the involuntary reflexive response of muscles is exploited in order to maximize the development of the muscles without requiring a voluntary exertion on the part of the subject.
A series of reflexive responses in the muscles can be stimulated by a continuous cycling of activations from a baseline input force to a peak input force and back to the baseline input force with the muscles being moved through a sufficient amplitude of displacement. The frequency of muscle activations according to the present invention is determined by the muscle""s stretch reflex time and the desired time interval between successive activations of the muscle. Because a muscle""s typical stretch reflex time is on the order of 20 milliseconds, many successive activations can be performed in a relatively short period of time, increasing the efficiency of muscle development according to the method of the present invention. Input of the desired activation force to the muscle can be achieved by moving the body or a portion of the body against its own weight and inertia, or by adding the input of an external force acting on the body.
In an aspect of the invention wherein the body""s own weight is used to provide the input force to the muscles, the body can be placed on a suitable drive mechanism. In an embodiment of the invention using the body""s own weight or inertia to provide the input force to the muscles, two stepping surfaces are disposed on a frame and adapted to be oscillatingly lifted and lowered in a push-pull fashion by means of a drive mechanism. The selected limbs of a human or other animal such as a race horse are placed on the stepping surfaces and a baseline input force determines the tone of the muscles in the limbs positioned on the stepping surfaces. The baseline tonus of the muscles can be varied by having the subject assume different positions on the stepping surfaces such as a partial squat position, and/or by placing an additional static mass on the subject. The stepping surfaces are moved to a predetermined peak amplitude over a predetermined period of time in order to stimulate the muscles"" natural involuntary reflexive response. The stepping surfaces are preferably moved out of synchronization with each other so that the body""s proprioception is accessed by an unconscious effort to avoid a shift of the center of gravity of the body. Alternating, vertical reciprocating motion of the stepping surfaces over a sufficient amplitude of displacement causes the reflexive responses in the muscles and stimulates the neural patterns characteristic of natural movement of the body such as walking or running.
Since most muscles involved in movement of the body have a response and decay time in the order of approximately 10 milliseconds, the activation frequency of the stepping surfaces is adapted to conform to the muscles"" natural reflexive response times. According to an aspect of the invention, a control device for controlling the drive mechanism is provided having an adjustable lifting frequency that can set the lifting frequency for the step surfaces to a value between approximately 1 and 60 Hz. More preferably, the device controls the frequency of activation between approximately 10 and 30 Hz. The amount of movement imparted to the muscles is also preferably set within the range of 2-50 mm, and more preferably 5-10 mm.
According to another aspect of the invention, the desired activation of the muscles in order to stimulate their natural involuntary reflexive responses can be achieved by superimposing oscillatory motion of an external mass onto a body""s voluntary movements. In accordance with this aspect of the invention, standard exercising equipment such as dumbbells, barbells, and other progressive resistance exercise machines including, but not limited to, machines sold under the trademarks xe2x80x9cUNIVERSAL,xe2x80x9d xe2x80x9cLIFECYCLExe2x80x9d and xe2x80x9cNAUTILUSxe2x80x9d can be modified to include the superimposed oscillatory motion. The input forces exerted on the muscles by the oscillating external mass can be provided along the same or different axes as the axes along which the progressive resistance is exerted.
Whether activation of the muscles is achieved by oscillatory motion of the body itself or by superimposing oscillatory motion of an external mass on the body, the frequency and amplitude of the oscillations are predetermined in order to stimulate the muscles"" natural involuntary reflexive responses or stretch reflexes. The desired frequency of activation (with one complete cycle including the time from a baseline input force to the peak force and back to the baseline force as well as the time before the next activation) is between approximately 1 and 60 Hz, and more preferably between 10 and 30 Hz. Furthermore, the amplitude of the oscillatory movement needed to achieve the desired results is in the range of approximately 2 to 50 mm., and more preferably in the range of approximately 5 to 10 mm.